This invention relates generally to injection molding and more particularly to an injection molding melt distribution manifold having an integral heated inlet portion.
Steel manifolds are mounted in an injection molding system and have a melt passage with a common inlet and a number of spaced outlets to distribute pressurized melt received from a molding machine to a number of different gates. Each system can have one or more manifolds with a variety of different configurations depending upon a number of factors, such as the number of gates, size and shape of the cavities, and type of material being molded. These manifolds are often heated to compensate for heat loss to the surrounding cooled cavity and back plates and maintain a more uniform temperature of the melt flowing through them. Gellert Canadian patent application serial number 2,017,055 filed May 17, 1990 entitled "Injection Molding Cast Manifold" shows an example of a manifold having an integral electrical heating element extending around a tortuous path.
Canadian application serial no. 2,017,055 also shows the manifold having an extension which extends rearwardly to receive melt from the molding machine. The manifold extension does not have a heating element and is fastened to the manifold by bolts. U.S. Pat. Nos. 4,669,971 to Gellert which issued Jun. 2, 1987 and 4,777,348 to Gellert which issued Oct. 11, 1988 disclose earlier examples of manifold extensions which are fastened to the manifold by screws. U.S. Pat. No. 4,438,325 to Gellert shows a heater cast which acts as a manifold extension and has a heating element separate from the heating element in the manifold. While this configuration is satisfactory for many applications, problems can arise in controlling the temperature of two different heating elements and in fastening the manifold extension to the manifold. Furthermore, the increasing demand for systems having greater numbers of gates has made compact component size even more critical.